1. Field of the Invention
The present invention relates to a recording tape cartridge including a case that houses a single reel onto which is wound a recording tape such as magnetic tape mainly used as a recording and playback medium for computers and the like.
2. Description of the Related Art
Conventionally, a recording tape cartridge has been known which includes a case that is made of synthetic resin and rotatably houses a single reel onto which is wound a recording tape such as magnetic tape used as a recording and playback medium for computers and the like. When the recording tape cartridge is in use (i.e., when it has been loaded into a drive device), the reel of the recording tape cartridge is rotatable within the case, and when the recording tape cartridge is not in use (i.e., when it has not been loaded into a drive device), the reel is locked to as to not be rotatable.
Namely, the recording tape cartridge is disposed with brake means for ensuring that the reel does not rotate inside the case when the recording tape cartridge is not in use. A configuration where, for example, a brake member that is not rotatable with respect to the case is made to engage with the reel is conceivable as the brake means.
For example, as shown in FIG. 20, a disc-shaped brake member 130 is housed inside a reel hub 112 of a reel 110 so as to be movable up and down. The reel hub 112 is formed as a bottomed cylinder. A pair of engagement protrusions 134 having a substantial “U” shape when seen in plan view are disposed on an upper surface of the brake member 130 so as to protrude from the upper surface of the brake member 130. A pair of rotation regulating ribs 126, which are disposed so as to extend downward from an inner surface of an upper case 122, are inserted in the engagement protrusions 134, so that the brake member 130 is not rotatable with respect to a case 120.
The brake member 130 is continually urged towards a bottom wall 114 of the reel hub 112 by an urging member such as a compression coil spring 116 so that an annular brake gear 132 formed on an undersurface of the brake member 130 is caused to mesh with an annular engagement gear 118 formed on an upper surface of the bottom wall 114 of the reel hub 112. Thus, inadvertent rotation of the reel 110 is prevented.
A substantially cylindrical operational protrusion 136 is disposed at an axial center portion of the undersurface of the brake member 130 so as to protrude from the undersurface of the brake member 130. The operational protrusion 136 is inserted in a through hole 114A disposed in an axial center portion of the bottom wall 114 of the reel hub 112, so that the operational protrusion 136 is exposed through a gear opening 128 disposed in a substantial center portion of a lower case 124. Thus, when the reel 110 is to be made rotatable, the operational protrusion 136 (i.e., the brake member 130) is pushed upward so that the brake gear 132 disengages from the engagement gear 118 (e.g., see U.S. Pat. No. 6,452,747).
However, in this configuration, when the recording tape cartridge is not in use, the reel 110 can rise upward (i.e., is movable in the axial direction of the reel 110) counter to the urging force of the urging member such as the compression coil spring 116. Thus, when the bottom wall 114 of the reel hub 112 is accidentally moves upward by an impact applied to the recording tape cartridge due to dropping thereof or the like, there are instances where, as shown in FIG. 20, the brake member 130 ends up being caught (falls) on the peripheral edge portion of the through hole 114A in a state where the brake member 130 is slanted.
There has been the problem that if the recording tape cartridge is loaded into the drive device in this state, recording and playback are impossible, and the potential arises for the recording tape cartridge to sustain damage and for the drive device to break down. There has also been the problem that the recording tape may be adversely affected, such as the recording tape becoming wrinkled or breaking, because the reel is rotatable when the recording tape cartridge is not in use.
Also, because the distance between the upper flange and the lower flange of the reel is substantially the same as the width of the recording tape, when the reel wobbles inside the case and the outer peripheral edges of the upper flange and lower flange strike the inner surface of the case and are deformed as a result of accidentally dropping the recording tape cartridge, there has been the problem that the recording tape is adversely affected, resulting in, for example, kinks in the recording tape.
A lock mechanism may conceivably be disposed on the inner surface of the top plate of the case to prevent the reel from rising (i.e., so that the reel becomes immovable in the axial direction) when the recording tape cartridge is not in use.
However, the case is assembled by bringing the peripheral walls of the upper case and the lower case into contact so that the upper case and the lower case are joined together, and ordinarily the inner surface of the top plate of the upper case is turned over to cover the lower case. Thus, when a lock mechanism is disposed on the inner surface of the top plate, there is the potential for the parts configuring the lock mechanism to fall out at the time the case is assembled. In other words, it is necessary to improve the incorporability of the lock mechanism in the case, and devices for this purpose have conventionally been a problem.